Dietary Pattern Associated With Reduced Alzheimer’s Disease Risk CME

For those of you who have a high incidence of Alzheimer’s in your family history (like me), here is some good news.  Paleolithic/ancestral eating seems to have some affect there.

April 23, 2010 — Individuals who consume a diet rich in nuts, fish, poultry, vegetables, fruits, and olive oil–based salad dressings but low in high-fat dairy products, red meat, organ meats, and butter have a reduced risk for Alzheimer’s disease, a new study suggests.

The finding, from a prospective community-based cohort study, warrants further exploration of food combinations in the prevention of this important public health problem, said lead study author Yian Gu, PhD, from the Taub Institute for Research in Alzheimer’s Disease and the Aging Brain, Columbia University, New York City.

“Many studies have looked at the relationship between diet and the risk of Alzheimer’s disease, but they have tended to focus on single nutrients or dietary items, such as fruits or vegetables or intake of meats. But the reality is that people eat a variety of foods, so we wanted to determine the best combination that might prevent Alzheimer’s,” she told Medscape Neurology.

Their results were published online April 12 in the Archives of Neurology. The study will also appear in the June issue of the journal.

Dietary Patterns

Dr. Gu and her colleagues studied a cohort of 2148 elderly subjects 65 years and older living in New York City. All subjects were healthy and free of dementia at study entry. Their dietary habits were obtained via questionnaire, and they were prospectively evaluated with the same standardized neurologic and neuropsychological measures approximately every 1.5 years for an average of 4 years.

The researchers used reduced rank regression to calculate dietary patterns according to their effect on 7 nutrients previously shown in the literature to be related to Alzheimer’s disease: saturated fatty acids, monounsaturated fatty acids, omega-3 polyunsaturated fatty acids, omega-6 polyunsaturated fatty acids, vitamin E, vitamin B₁₂, and folate.

During the follow-up, 253 individuals developed Alzheimer’s disease. The study found that one dietary pattern — characterized by higher intakes of salad dressing, nuts, fish, tomatoes, poultry, cruciferous vegetables, fruits, and dark and green leafy vegetables and a lower intake of high-fat dairy products, red meat, organ meat, and butter — was significantly associated with a reduced risk for Alzheimer’s disease.

Compared with subjects in the lowest tertile of adherence to this pattern, the Alzheimer’s disease hazard ratio (95% confidence interval) for subjects in the highest tertile was 0.62 (0.43 – 0.89) after multivariable adjustment (P for trend = .01).

The study also found that subjects who were older, less educated, and current smokers tended to be less adherent to the protective diet. Hispanic individuals adhered less than white and black individuals (P = .02), and women tended to adhere more than men (P = .05).

“The dietary pattern that was most protective against Alzheimer’s reflected a diet rich in ω-3 and ω-6 polyunsaturated fatty acids, vitamin E, and folate but poor in saturated fatty acids and vitamin B₁₂,” commented Dr. Gu. “The combination of nutrients in this dietary pattern reflects multiple pathways in the development of Alzheimer’s disease.

“For example, vitamin B₁₂ and folate are homocysteine-related vitamins that may have an impact on the disease through their ability to lower circulating homocysteine levels,” she said. “Vitamin E is a strong antioxidant, and the fatty acids may be linked to dementia and cognitive function through atherosclerosis, thrombosis, or inflammation. Fatty acids may also affect brain development and membrane functioning.”

She added that the study has several limitations. “We used a single measurement of the diet, and this might not have captured the long-term dietary habits of the subjects. We also excluded subjects from the final analysis because they were lost to follow-up, and this might have introduced selection bias. We also can’t completely rule out the possibility that the reduced risk associated with this protective diet was due to residual confounding.”

Further studies are planned, Dr. Gu said. “We cannot say based on this study alone that this type of dietary pattern prevents Alzheimer’s disease, but many studies have consistently shown that fruits and vegetables and unsaturated fatty acids are associated with a lower risk. We want to repeat these findings in different populations and see if they can be confirmed in other studies.”

Array of Health Behaviors

Commenting on this study for Medscape Neurology, David Knopman, MD, professor of neurology at the Mayo Clinic and a member of the Mayo Clinic Alzheimer’s Disease Research Center in Rochester, Minnesota, said that, despite the study authors’ best efforts, it is still not clear whether diet alone makes a difference.

“Dietary habits, which often are lifelong, are certainly part of the array of health behaviors that contribute to better cognitive health in late life. However, diet and other health behaviors are intertwined. Because a healthy diet contributes to better cardiac health, lower weight, lower blood pressure and a lower risk for diabetes, there are many reasons to view the dietary habits described by Dr. Gu and colleagues as beneficial.”

The study was supported by federal National Institute on Aging grants. Dr. Gu and Dr. Knopman have disclosed no relevant financial relationships.

Arch Neurol. Published online April 12, 2010.

Clinical Context

There is increasing evidence linking Alzheimer’s disease to diet intake, but the impact of particular nutrients on risk is uncertain. For example, adherence to the Mediterranean diet has been linked with a lower risk for Alzheimer’s disease, but only a limited number of food groups are considered in the Mediterranean diet.

This is a prospective cohort study of a longitudinal cohort of community-dwelling elderly residents of New York City without dementia at baseline to examine the link between dietary pattern analyzed by reduced rank regression to derive a pattern consistent with reduced risk.

Study Highlights

• 2148 elderly subjects 65 years and older were recruited from among a sample of Medicare beneficiaries. Baseline standardized history, physical examination, and neuropsychological test batteries were performed.
• A global summary score on the Clinical Dementia Rating was obtained at baseline, and subjects were monitored at 1.5-year intervals for testing.
• Average food consumption in the year before the testing was obtained by a 61-item version of the Willet semiquantitative food frequency questionnaire by trained interviewers in English or Spanish.
• The nutrient intake from foods consumed was calculated and then used in the reduced rank regression analysis.
• At the 1.5-year interval examinations, status of possible or probable Alzheimer’s disease was determined by criteria of the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer Disease and Related Disorders Association.
• Reduced rank regression determines linear combinations (ie, scores of dietary patterns) of a set of predicting variables. This test was performed with use of 30 predetermined food groups.
• The nutrients used in the analysis were saturated fatty acids, monounsaturated fatty acids, omega-3 polyunsaturated acids, omega-6 polyunsaturated fatty acids, vitamin E, vitamin B₁₂, and folate.
• This list was generated from what was most commonly reported as associated with Alzheimer’s disease risk in the literature.
• A dietary pattern score was calculated for every pattern that emerged, for a total of 7 groups of dietary pattern scores.
• After an average follow-up of 3.96 years, 253 incident cases of Alzheimer’s disease were identified.
• The participants who went on to have Alzheimer’s disease were older, were less educated, and had lower body mass index vs those without Alzheimer’s disease.
• They were more likely to be Hispanic than white and were less likely to consume moderate alcohol.
• The 7 dietary pattern scores examined explained 76.8% and 29.5% of the total variation in nutrient and food intakes, respectively.
• The crude hazard ratios for Alzheimer’s disease in the highest vs the lowest tertiles for the dietary patterns 1 though 7, respectively, were 1.06, 0.54, 1.10, 1.16, 0.94, and 0.96.
• Dietary pattern score 2 was the only pattern that was associated with Alzheimer’s disease risk; therefore, subsequent analysis focused on this pattern.
• A high dietary pattern score 2 indicated a diet rich in omega-3 polyunsaturated fatty acids, omega-6 polyunsaturated fatty acids, vitamin E, and folate (all positively correlated, P < .001) but poor in saturated fatty acids and vitamin B₁₂.
• Dietary pattern score 2 correlated positively with intakes of salad dressing, nuts, fish, tomatoes, poultry, cruciferous vegetables, fruits, and dark and leafy vegetables.
• This score correlated negatively with intakes of high-fat dairy, red meat, organ meat, and butter.
• Subjects who were older, less educated, and current smokers were less likely to adhere to dietary pattern score 2.
• Compared with subjects in the lowest tertile of adherence to dietary pattern score 2, those in the middle and highest tertiles, respectively, had a 19% and 38% lower risk for Alzheimer’s disease (P for trend = .01).
• Alcohol intake and nutrient supplements did not affect this association.
• The authors concluded that a dietary pattern rich in omega-3 polyunsaturated fatty acids, omega-6 polyunsaturated fatty acids, vitamin E, and folate and poor in saturated fatty acids and vitamin B₁₂ was associated with a lower risk for Alzheimer’s disease in older persons.

Clinical Implications

• The risk for Alzheimer’s disease is lower by 19% and 38%, respectively, for individuals in the middle and highest vs the lowest tertiles of adherence to dietary pattern score 2.
• The dietary pattern protective against Alzheimer’s disease consists of a diet rich in salad dressing, nuts, fish, tomatoes, poultry, cruciferous vegetables, fruits, and dark and leafy vegetables and low in high-fat dairy, red meat, organ meat, and butter.